1. Field of the Invention
The present invention relates to an airbag apparatus for a front passenger seat for protecting a passenger sitting in the front passenger seat upon collision of a vehicle, such as a car, to thereby ensure safety of the passenger. More particularly, the invention relates to an improvement in the structure of a fracture-opening section formed on the cover of an instrument panel in opposition to an airbag accommodated within an airbag apparatus for a front passenger seat which, in turn, is accommodated within the instrument panel. Upon collision of the vehicle, the airbag,inflates out of the instrument panel while breaking open the fracture-opening section, so as to protect the passenger.
2. Description of the Related Art
An airbag apparatus for a front passenger seat of a vehicle, such as a car, basically includes an airbag, an airbag case for accommodating the folded airbag, and an inflater for inflating the airbag. The airbag apparatus is accommodated within an instrument panel in opposition to the front passenger seat.
The instrument panel cover includes a cover plate having a size corresponding to that of an opening portion of the airbag case as disclosed in Japanese Patent Application Laid-Open (kokai) No. 7-172256 or includes a lid plate as proposed by the inventors of the present invention in Japanese Patent Application No. 10-7979. According to Japanese Patent Application No. 10-7979, the lid plate is located in opposition to the opening portion of the airbag case and is formed integrally with the instrument panel cover. The main body of a lid reinforcement is fixedly attached to the lid plate from inside along a peripheral edge portion of the lid plate. A portion of the reinforcement which extends from a hinge portion of the reinforcement extending upward from the main body of the reinforcement is fixedly attached to the airbag case via a bracket. Upon inflation of the airbag, the cover plate or the lid plate is opened.
The thus-configured airbag apparatus for a front passenger seat functions in the following manner. Upon collision of the vehicle, an impact force caused by the collision is detected by a sensor. A control unit including a CPU judges whether or not the detected impact force is equal to or higher than a predetermined value. When the control unit judges that the impact force is not lower than the predetermined value, the control unit issues a signal for causing the inflater to generate a predetermined gas. The gas is fed to the airbag so as to promptly inflate the airbag.
The inflating airbag presses, from inside, a fracture-opening lid, such as the cover plate or the lid plate, of the instrument panel cover. The lid is fractured along a fracture line and detached from the instrument panel cover. The detached lid is opened outward while being turned inside out about the hinge portion of the lid reinforcement.
The inflating airbag projects outward from the instrument panel cover through the thus-formed opening in the instrument panel cover. Serving as a cushion, the inflated airbag supports a front seat passenger at his/her chest and head, thereby protecting the passenger from the impact force of collision.
Generally, the conventional instrument panel of a vehicle has a fracture-opening lid formed thereon in such a manner as to face the front passenger seat of the vehicle; i.e., the lid is formed on an inclined plane of the instrument panel which faces a front seat passenger. Upon inflation of the airbag, the fracture-opening lid is detached from the inclined plane. The detached lid is opened outward while being turned inside out about the hinge portion of the lid reinforcement. The inflating airbag projects outward from the instrument panel. An edge of the thus-detached lid may injure the front seat passenger. When the passenger is a child, detachment of the lid occurs in the vicinity of the face of the child, thus doubling the degree of danger.
In order to prevent the above danger, an airbag apparatus for a front passenger seat as shown in FIG. 1 has been developed.
An airbag apparatus for a front passenger seat 1 shown in FIG. 1 is disposed within an instrument panel such that an airbag 4 inflated by means of gas from an inflater projects from a substantially horizontal plane 3a of an instrument panel cover 3 located in the vicinity of a windshield la of a vehicle. The airbag apparatus includes an airbag case 5 adapted to accommodate the folded airbag 4 and having an opening portion 5a formed in opposition to the back surface of the instrument panel cover 3. A flexible fracture-opening lid 6 formed of a synthetic resin is disposed at an opening portion 3b formed on the instrument panel cover 3 in opposition to the opening portion 5a of the airbag case 5. Upon inflation of the airbag 4, the fracture-opening lid 6 is split open into two fracture pieces, which open apart in opposite directions toward the front and rear of the vehicle, respectively, through fracture along grooves 6a and 6b, which are formed along the centerline of and the periphery of the fracture-opening lid 6 and serve as fragile portions. The inflating airbag 4 projects outward through the thus-formed opening.
A mounting leg portion 7 and a plurality of engagement pieces 8 are integrally formed on the back surface of the fracture-opening lid 6. The mounting leg portion 7 assumes the form of a rectangular frame slightly greater in size than the opening portion 5a of the airbag case 5. The engagement pieces 8 are elastically engaged with the edge of the opening portion 3b of the instrument panel cover 3. A plurality of rectangular through-holes 7c are formed in a front wall 7a of and in a rear wall 7b of the mounting leg portion 7. When the fracture-opening lid 6 is fitted to the opening portion 3b of the instrument panel cover 3, the rectangular through-holes 7c are engaged with corresponding hooks 9 fixedly attached to a front wall 5b of and to a rear wall 5b of the opening portion 5a of the airbag case 5.
Upon inflation of the airbag 4, the fracture-opening lid 6 is split open into two fracture pieces, which open apart in opposite directions toward the front and rear of the vehicle, respectively, through fracture along the grooves 6a and 6b, which are formed along the centerline of and the periphery of the fracture-opening lid 6. Since the rectangular through-holes 7c formed in the front and rear walls 7a and 7c of the mounting leg portion 7 are engaged with the hooks 9 fixedly attached to the front and rear walls 5b of the opening portion 5a of the airbag case 5, scattering of the fracture pieces of the fracture-opening lid 6 is prevented.
According to the airbag apparatus for a front passenger seat shown in FIG. 1, the opening portion 3b is formed in the instrument panel cover 3 in such a manner as to face the opening portion 5a of the airbag case 5. The fracture-opening lid 6 is a discrete element different from the instrument panel cover 3 and made of a flexible resin material and is fitted into the opening portion 3b. Thus, the manufacture and the assembly work of the instrument panel cover 3 and the fracture-opening lid 6 are rather complicated. Also, the fracture-opening lid 6 easily deforms when an external force is applied thereto, thereby damaging the appearance or design of the instrument panel cover 3.
Also, the discrete fracture-opening lid 6 is not reinforced from behind. Since the fracture-opening lid 6 is made of a flexible material, upon inflation of the airbag 4, the leg portion 7 is likely to disengage from the hooks 9 fixedly attached to the front and rear walls 5b of the opening portion 5a of the airbag case 5, potentially involving scattering of fracture pieces of the fracture-opening lid 6.
An object of the present invention is to solve the above-mentioned problems in the conventional airbag apparatus for a front passenger seat and to provide an airbag apparatus for a front passenger seat which can be manufactured and assembled easily, whose fracture-opening section can be fractured reliably upon inflation of an airbag while maintaining high safety, and which has an improved appearance.
In order to achieve the above object, the present invention provides an airbag apparatus for a front passenger seat built in an instrument panel of a vehicle, comprising: an airbag case accommodated within a core of the instrument panel and having an opening portion located in opposition to a back surface of a cover of the instrument panel; an airbag accommodated within the airbag case in a folded state, the airbag being able to be inflated by means of gas from an inflater; a fracture-opening section defined in the cover to be located in opposition to the opening portion of the airbag case, the fracture-opening section having a fragile contour portion surrounding the fracture-opening section and a fragile splitting portion for dividing t he fracture-opening section into first and second subsections; and first and second reinforcements fixedly attached to back surfaces of the first and second subsections, each of the first and second reinforcements having a hinge portion and a leg portion whose end is engaged with a hook fixedly attached to the opening portion of the airbag case, whereby the fracture-opening section opens apart along the fragile splitting portion upon inflation of the airbag.
The above configuration facilitates manufacture, allows the fracture-opening section to be reliably fractured along the contour portion and the splitting portion while maintaining high safety, and imparts favorable appearance or de sign to the instrument panel.